1. Field of the Invention
The invention relates to secure digital cards, and more particularly to bank-connection payments using the secure digital cards.
2. Description of the Related Art
An ordinary cell phone can perform a bank-connection payment with a secure digital card. Ordinarily, bank-connection payment processes are divided into near-end payment processes and far-end payment processes. When the user of a cell phone performs a near-end payment process, a near field communication (NFC) controller of the cell phone completes a financial transaction between the cell phone and a point of sale (POS) according to a near field communication protocol. When the user of the cell phone performs a far-end payment process, a payment application of the cell phone is used to complete a bank-connection payment.
No matter whether the user of the cell phone performs the near-end payment process or the far-end payment process, the cell phone needs to perform a bank-connection payment transaction with a secure digital card. Ordinarily, the secure digital card comprises a smart card for storing data about the bank-connection payment transaction. Because the smart card has data encryption capability and data processing capability, the smart card is suitable for storing bank-connection payment data. When the user of the cell phone performs a near-end payment process, an NFC controller of the cell phone supplies power to the smart card. When the user of the cell phone performs a far-end payment process, a secure digital card controller (SDC) supplies power to the smart card. Thus, the secure digital card must switch the power supplied to the smart card according to whether the user of the cell phone performs the far-end payment process or the near-end payment process.
Ordinarily, the NFC controller generates a voltage level of 3V or 1.8V to be supplied to the smart card, and the SDC generates a voltage level of 3.3 V to be supplied to the smart card. Because the voltage of 3.3V generated by the SDC is higher than the voltage of 3V or 1.8V generated by the NFC controller of the cell phone, when the SDC switches the power source of the smart card, the SDC must prevent the voltage of 3.3V generated by the SDC from surging to the NFC controller of the cell phone. Otherwise, the NFC controller of the cell phone may be damaged. Thus, a new type of secure digital card is required.